1. Field of the Invention
The present invention relates to a rotary cutter unit having a mechanism for detecting a waiting position of the unit, and a printer device having the rotary cutter unit.
2. Description of the Related Art
In a conventional printer, printing paper unwound from a roll of paper is nipped between a platen roller and a thermal head, and printing is carried out by heating the thermal head during the feeding of the paper. In some printers, a cutter having a V-shaped blade or a spiral blade is provided for cutting printing paper after printing. When a rotary cutter, having a spiral blade formed on a cylindrical rotating body, is arranged in a printer, the printer may be more compact than a printer having another type of cutter such as the V-shaped cutter. For example, Japanese Unexamined Patent Publication (Kokai) No. 2-167696 discloses a control device for cutting a sheet, having a detecting member 9 attached to the side of a knife rotor 4 and a detection sensor 10 capable of transmitting a stop command when detecting member 9 is positioned where the detecting member cannot be detected during deceleration, so that knife 8 does not stop at a position where the knife can cut a sheet.
Japanese Examined Utility Model Publication (Kokoku) No. 7-1272 discloses a rotary cutter device, in which a disk 5 having a notch 5a formed thereon is attached to a rotation shaft of a rotating blade 1 and a photosensor 6 detects the position of notch 5a, whereby rotating blade 1 may be stopped at a rotational position within a predetermined range.
In a rotary cutter having a fixed blade and a rotating blade, when the blades contact each other or are positioned close to each other, it is difficult to smoothly insert printing paper between the blades, which may result in a paper jam. Therefore, when the rotating blade is stopped, it is necessary to control the stopping position of the rotating blade so that an edge of the rotating blade is away from the fixed blade by a certain distance (in other words, the rotating blade is positioned at a waiting position, a so-called “a home position”). In both Japanese Unexamined Patent Publication (Kokai) No. 2-167696 and Japanese Examined Utility Model Publication (Kokoku) No. 7-1272, it is possible to stop the rotating blade at the home position. However in recent years, a more compact printer, having a function for detecting the rotational position of the rotating blade has been desirable.
For example, in the printer of Japanese Examined Utility Model Publication (Kokoku) No. 7-1272, disk 5 and photosensor 6 for detecting the rotational position of rotating blade 1 are arranged outside of rotating blade 1 in relation to the axial direction of the rotating blade, and therefore the printer inevitably has a wide width due to the volumes of disk 5a and photosensor 6.